Module 15: Testing

Practice Tasks

Complete these tasks to reinforce what you learned in this module.

Task 1: Write a unit test

The function double is defined for you in the editor. Replace the placeholder body of test_double with real assertions: double(5) == 10 and double(0) == 0.

Expected Output:

`cargo test` passes (`test_double` goes from failing to passing).

Hint: Use assert_eq!(double(5), 10); and assert_eq!(double(0), 0); inside the #[test] fn test_double().

Starter Code:

task.rs

// Task 1: write a unit test for `double`. Fill in the test below, then press
// "Check" — this task is graded by running `cargo test`. See tasks/TASKS.md.

pub fn double(n: i32) -> i32 {
    n * 2
}

fn main() {
    // `cargo test` ignores main; it's here only so this file also builds as a binary.
    println!("double(5) = {}", double(5));
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_double() {
        // YOUR CODE HERE: assert that double(5) == 10 and double(0) == 0.
        todo!("write the assertions with assert_eq!");
    }
}

Task 2: assert! and the negation operator

The function is_positive is defined for you. Replace the two placeholder tests: test_positive should assert!(is_positive(1)), and test_negative should assert!(!is_positive(-1)).

Expected Output:

`cargo test` passes both `test_positive` and `test_negative`.

Hint: assert!(cond) fails if cond is false. For the negative case, assert the negation: assert!(!is_positive(-1));.

Starter Code:

task.rs

// Task 2: write tests using assert! for `is_positive`. Fill in the two tests
// below, then press "Check" (graded by `cargo test`). See tasks/TASKS.md.

pub fn is_positive(n: i32) -> bool {
    n > 0
}

fn main() {
    println!("is_positive(1) = {}", is_positive(1));
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_positive() {
        // YOUR CODE HERE: assert!(is_positive(1))
        todo!("assert that is_positive(1) is true");
    }

    #[test]
    fn test_negative() {
        // YOUR CODE HERE: assert!(!is_positive(-1))
        todo!("assert that is_positive(-1) is false");
    }
}

// Task 1: write a unit test for `double`. Fill in the test below, then press // "Check" — this task is graded by running `cargo test`. See tasks/TASKS.md. pub fn double(n: i32) -> i32 { n * 2 } fn main() { // `cargo test` ignores main; it's here only so this file also builds as a binary. println!("double(5) = {}", double(5)); } #[cfg(test)] mod tests { use super::*; #[test] fn test_double() { // YOUR CODE HERE: assert that double(5) == 10 and double(0) == 0. todo!("write the assertions with assert_eq!"); } }

// Task 2: write tests using assert! for `is_positive`. Fill in the two tests // below, then press "Check" (graded by `cargo test`). See tasks/TASKS.md. pub fn is_positive(n: i32) -> bool { n > 0 } fn main() { println!("is_positive(1) = {}", is_positive(1)); } #[cfg(test)] mod tests { use super::*; #[test] fn test_positive() { // YOUR CODE HERE: assert!(is_positive(1)) todo!("assert that is_positive(1) is true"); } #[test] fn test_negative() { // YOUR CODE HERE: assert!(!is_positive(-1)) todo!("assert that is_positive(-1) is false"); } }